US President Barack Obama on Monday called on Russia to join him as an equal partner in updating a nuclear non-proliferation deal, after Moscow opted not to extend it earlier this year.

Russian officials said in October that they had notified Washington that the Nunn-Lugar program, which disposed of thousands of Soviet-era warheads and missiles, would not be extended when it expires in May.

The decision was seen as the latest challenge to the "reset" of relations Obama engineered with Russia early in his first term, ties that are now in a new era under the returning President Vladimir Putin.

But Obama said Monday that he was ready to talk to Russia about a new version of the 20-year pact, as he honored its founders, Republican Senator Richard Lugar and former Democratic senator Sam Nunn.

"Russia has said that our current agreement hasn't kept pace with the changing relationship between our countries," Obama said at the event in Washington.

"To which we say, let's update it. Let's work with Russia as an equal partner. Let's continue the work that's so important to the security of both our countries. And I'm optimistic that we can."

US diplomats started talking to Russia about renewing the US-financed program in July, but Deputy Russian Foreign Minister Sergei Ryabkov said Moscow wanted to end it.

Lugar, who is leaving the Senate after losing a Republican primary challenge, traveled to Russia in August to talk about extending the deal.

The Nunn-Lugar plan was created in 1992 after the breakup of the Soviet Union amid worries over the fate of its vast arsenal of nuclear as well as chemical and biological weapons.

It began with an effort to safeguard materials by improving security at nuclear complexes and graduated to decommissioning work.

Ryabkov suggested that Moscow was starting to feel constrained by the deal because it gave Washington access to sensitive information about its weapons that Moscow could not get about America's nuclear arsenal.

Lugar says the scheme has deactivated 7,610 strategic nuclear warheads and destroyed 902 intercontinental ballistic missiles and 906 nuclear air-to-surface missiles along with 684 submarine-launched ballistic missiles, among other stockpiles that have been eliminated.

The decision not to renew the Nunn-Lugar program came weeks after the Kremlin asked a key US democracy development organization to leave Moscow in the latest deterioration in relations under Putin.

USAID was ordered out of the country over accusations it supported opposition leaders who helped organize a wave of demonstrations against Putin.